cross-sport/career-twin-curves.ts (S249) — pure geometry for the Career Twins overlay.
Kept out of the component so the load-bearing decision is testable on its own: twins are cross-sport AND cross-era by construction, so the curves are aligned by CAREER YEAR (1..N) rather than calendar year. Plotting real dates would put a 1946 career and a 2016 career in different halves of the chart and compare nothing.
A gap in the rated seasons does NOT consume a career-year slot: an unmeasured season is missing evidence, not a season of zero dominance, so it must not stretch the axis.